Electropositive means electron donating.The transition elements can donate valence electrons in ns sub-shell and the electrons in (n-1)d sub-shell and are thus electropositive in nature.
Metallic atoms have a very special kind of bond called the metallic bond, where the electrons, instead of remaining with a particular atoms, they create an electron cloud which roams around the ions. The ions don't own any significant electrons, instead, they own an electron cloud which is shared by them all.
As electrons move about almost freely in the form of a cloud, metals conduct electricity.
The reason behind the luster is also the metallic bond.
The metallic ions remain as crystals and each metal has a particular crystal structure (e.g. Cubic, Body centered cubic, face centered cubic, hexagonal etc)
Sound is created as a result of vibration. When any external impact force is applied, the atoms vibrate to a particular extent and sound in produced.
That's the reason of the sonorosity.
The closed packed structure in metals are such that, dislocation movement is easy. Due to easier dislocation motion, metals are ductile and malleable.